Re: 1997 Volvo S90 crank but no start
"ojm8183" <email@example.com> wrote in message
> 1997 Volvo S 90 cranks but doesn't start. I have replaced the RPM sensor,
> have tried replacing the engine computer with a known good one but it
> would not start. I have no spark and no injector pulse. The car will start
> after many long cranking tries. The car has about 75,000 miles. I am an
> ASE master mechanic with many years experience and this once has me
> stumped. Any suggestions what might be the problem. Could it be the
> coolant sensor even though the one in there test fine? I have tried
> replacing the coolant sensor and am still having the same problem, any
> ideas, thoughts, spells that will make this car run???/
To be quite honest, you are not a very good master mechanic if you cannot
solve a basic ECU power / primary igntion problem.
Check and replace the main relay, and check the ECU is powered up and has
good ground on the relevant pins.
If that is ok, which RPM sensor did you replace? There are two. Flywheel and
cam sensor. You need both working.
A dud CTS or break in the wiring will not prevent the ecu from fueling- it
will default to a fixed value. This is fundemental knowledge.